Abstract: Volume II/25 is a supplemented and revised edition of the preceding volumes II/7, II/15, II/21 and II/23 containing up to date information on inorganic and organic polyatomic molecules. All experimental methods for the determination of quantitative structural data of free molecules have been considered: microwave, infrared, Raman, electronic and photoelectron spectroscopy as well as electron diffraction. The data obtained by these methods have been critically evaluated and compiled. They are presented separately for each molecule, together with a schematic figure of the structure and the original literature.